The present invention relates to a latex polymer of fine particles useful in applications such as silver halide photographic light-sensitive materials, paints and varnishes and adhesives.
The present invention also relates to a silver halide photographic light-sensitive material and more specifically to a silver halide photographic light-sensitive material containing a novel latex polymer. More specifically, the present invention relates to a silver halide photographic light-sensitive material improved in physical properties of films without impairing photographic properties, through the use of the latex polymer.
The present invention further relates to a method for forming images on a silver halide photographic light-sensitive material which permits the formation of high contrast images at a pH of less than 11.0 and more particularly to an image-forming method which requires only a small amount of developer to be supplemented.
As the active methylene group can react with amino groups, isocyanates and melamines to form covalent bonds, there have long been proposed various applications of polymers having reactive groups on the side chains thereof which are formed through homopolymerization of ethylenically unsaturated monomers carrying active methylene groups or copolymerization thereof with various other ethylenically unsaturated monomers.
On the one hand, gelatin is generally and widely used as a binder in the hydrophilic colloidal layer constituting the photographic light-sensitive material. Gelatin is a binder having quite excellent characteristic properties. For instance, it has high swelling and gelling abilities and can easily be crosslinked with a variety of film-hardening agent.
On the other hand, if gelatin is used as an ingredient for forming the hydrophilic colloidal layer, it can not always impart satisfactory physical properties to the resulting film. For instance, it suffers from problems such as deformation due to plastication of the film under high humidity conditions, extension of the film due to absorption of moisture or brittleness of the film under low humidity conditions.
In order to eliminate such drawbacks of the gelatin film, there have been proposed many attempts to improve of, for instance, the dimensional stability against humidity, scratch resistance, brittleness and drying characteristics of hydrophilic colloidal films by incorporating a latex polymer into the hydrophilic colloidal layers such as silver halide emulsion layers, protective layers, backing layers and intermediate layers.
For instance, U.S. Pat. Nos. 2,763,625 and 2,852,382, Japanese Un-Examined Patent Publication (hereinafter referred to as "J.P. KOKAI") Nos. Sho 62-115152, Hei 5-66512 and Hei 5-80449 and Japanese Examined Patent Publication (hereinafter referred to as "J.P. KOKOKU") Nos. Sho 60-15935, Hei 4-64058 and Hei 5-45014 disclose the use of latex polymeres derived from a variety of monomers represented by alkyl acrylates and alkyl methacrylate in gelatin-containing hydrophilic colloidal layers.
The use of the latex of this type is effective in the improvement of some characteristic properties of the gelatin film, but the resulting gelatin film is insufficient in the strength under, in particular, high humidity conditions or water-containing state. Incidentally, it has been known that such problems can be solved by incorporating, into the latex, active methylene groups reactive with gelatin or coexisting film-hardening agents, through copolymerization.
For instance, J.P. KOKOKU Nos. Sho 45-5819 and Sho 46-22507 and J.P. KOKAI No. Sho 50-73625 disclose that, in photographic light-sensitive materials, the wear resistance and hardness of a latex-containing gelatin film (in particular, these properties thereof in wet conditions) are improved by incorporating, into a gelatin film, a latex polymer obtained by copolymerizing a monomer carrying an active methylene group such as 2-acetoacetoxyethyl methacrylate or 2-cyanoacetoxyethyl methacrylate with a monomer such as an alkyl acrylate.
However, more than a certain amount of the active methylene-containing monomer must be copolymerized for preparing the foregoing latex used for improving the wear resistance and hardness of the gelatin film to a desired level.
Moreover, if the ratio of the latex to gelatin increases or the absolute quantity of gelatin is reduced, the strength of the resulting gelatin film in a wet state is considerably reduced. As a result, the amount of the active methylene-containing monomer to be copolymerized must be further increased or any gelatin film having a desired strength cannot be obtained by simply increasing the amount of the active methylene-containing monomer.
The reduction in the coated amount of gelatin has become an important subject in recent photographic light-sensitive materials, from the viewpoint of obtaining high quality images, requirements for highly improved physical properties of films and speeding up of the processing of the materials. In the field of phototype process, for instance, there has intensively been desired for the improvement in the dimensional stability of the photographic light-sensitive material by reducing the amount of gelatin to be used in the material or for the reduction of the amount of processing solutions to be supplemented by reducing the amount of the processing solutions carried over by the material during processing.
Therefore, these films having low gelatin contents and gelatin films comprising a large amount of such a latex suffer from problems such that the film strength is sometimes insufficiently improved through the incorporation of a latex conventionally obtained by simply copolymerizing an active methylene-containing monomer and that the production cost of such a latex polymer increases due to the use of a large amount of an active methylene-containing monomer having a relatively complicated structure. Accordingly, there has been desired for further improvement.
Moreover, J.P. KOKAI No. Hei 5-295302, European Patent Laid-Open (hereinafter referred to as "EPLO") No. 501666, International Un-Examined Patent Publication (hereinafter referred to as "KOHYO") No. 93-16133 disclose that copolymers of active methylene-containing monomers exhibit excellent properties as latexes for use in paints and varnishes such as water resistance, resistance to saline solutions and resistance to alkalis and J.P. KOKAI Nos. Hei 4-253784, Hei 5-194914 and Hei 5-287248, EPLO No. 573142 or the like disclose that latex copolymeres of active methylene-containing monomers exhibit excellent properties as latexes for use in adhesives such as adhesion strength and water resistance.
Toshihiko NAKAMICHI, Coloring Materials, 1992, 65, pp. 511-525 discloses that the copolymers of active methylene-containing monomers form three-dimensionally crosslinked films if they are used in combination with various additives and it can be appreciated that the effects of the copolymers of active methylene-containing monomers on the foregoing fields of paints and varnishes and adhesives are accomplished by the crosslinking reaction.
In these fields, however, there has also been desired for the development of materials which can impart more excellent properties to the resulting product while using the same amount of an active methylene-containing monomer, from both quality and economical standpoints.
On the other hand, as examples of latex polymeres having core/shell dual structures, J.P. KOKAI No. Sho 58-42044 discloses silver halide color photographic light-sensitive materials comprising core/shell latexes whose shell portion consists of a polymer containing coupler units capable of forming a dye through coupling with an oxidized developing agent and also discloses pivaloylacetanilide type or benzoylacetanilide type couplers as specific examples of yellow couplers.
However, the core/shell latex polymeres disclosed in this patent suffer from the following problems:
(i) The rate of the core comprising a non-dye-forming monomer is very low (at most 10%, among the compounds listed). Therefore, the concentration of the active methylene moieties on the shell side through the formation of a core/shell structure does not ensure the foregoing various merits so much. The foregoing rate of the core portion is quite insufficient while taking into consideration the fact that it is effective for, for instance, reducing the thickness of light-sensitive materials to increase the content of coupler monomer units as high as possible, in the field of polymer couplers. PA0 (ii) The reactivity of a compound having an active methylene structure which is sterically complicated beyond a certain level such as pivaloylacetoanilide or benzoylacetoanilide is not necessarily sufficient and must be further improved from the viewpoint of, for instance, the effect of improving the strength of gelatin films.
In addition, this patent does not disclose the use of a conjugated diene monomer as a material for the core particles and the usefulness thereof.
On the other hand, in the field of recent graphic arts, the printing process is apt to be complicated as the color printing has widely been employed. There has been increased a demand for reducing the appointed date of delivery since much importance has been attracted to the immediate availability of information.
In compliance with such a demand, there has been proposed a method in which a film for plate-making by printing is processed with a developer undergoing only a small variation in pH to stabilize the developing process and to thus stabilize the precision of the overall plate-making process. It has been known that any change in the quality of photographs can be reduced by minimizing the variation in pH of the developer. For instance, J.P. KOKOKU No. Hei 3-5730 discloses a method for stabilizing the quality of photographs by improving the buffering ability of the developer.
However, if the buffering ability of the developer is improved by increasing a salt concentration, the hydrophilic colloidal layer is not sufficiently swollen and accordingly, this process does not provide photographs showing high contrast. Moreover, in the light-sensitive material whose hydrophilic colloidal layer comprises a dye or a pigment, a problem arises, such as severe remaining color stain.
It has been known that the developer is supplied in the form of a solid processing agent. For instance, J.P. KOKAI No. Sho 61-259921 discloses a method for improving the stability of a solid processing agent as a developer.